This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2001-193275, filed Jun. 26, 2001; and No. 2001-199134, filed Jun. 29, 2001, the entire contents of both of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an apparatus for reading an object to be detected and, more particularly, to a reading apparatus which is used in a living body authentication system and is used to read an object to be detected such as a fingerprint that specifies an individual.
2. Description of the Related Art
As a reading apparatus for reading a fingerprint pattern based on the fine three-dimensional pattern of a fingertip of a person to be examined, a fingerprint reader is known. The fingerprint reader comprises a sensor device which has a sensor unit for reading the fingerprint of the fingertip, and a driver circuit unit which is arranged near the sensor unit and supplies a drive signal for driving the sensor unit to the sensor unit.
Such fingerprint readers include a reader which can read fingerprints when a person touches the sensor unit with a fingertip and optically recognizing the three-dimensional pattern of skin that forms the fingerprint, and a reader which reads a change in capacitance or resistance in correspondence with the three-dimensional pattern of a finger.
Note that a human finger is often charged with electricity, and when such person touches an object with a finger, the charged static electricity as high as several thousand volts is often discharged instantly.
In some cases, the driver circuit unit of the fingerprint reader is electrically connected to and neighbors the aforementioned sensor unit on a single circuit board to attain high-density packaging. When a finger touches such fingerprint reader, the distance between the finger and the sensor unit or driver circuit unit becomes short, and a voltage of static electricity is applied to the sensor unit or driver circuit unit via an insulating film that covers the sensor unit and driver circuit unit, thus causing operation errors and/or damage.
The driver circuit unit is made up of many transistors. Amorphous silicon or polysilicon can be used as a semiconductor layer of such a transistor. Amorphous silicon or polysilicon is excited by visible light in its nature. On the other hand, since an uppermost insulating film of the driver circuit unit is normally formed of a light transmission material, when the driver circuit unit is exposed to intense external light, electron-hole pairs are generated in the semiconductor layer of the transistor, and these carriers may cause operation errors of the driver circuit unit.
It is an object of the present invention to provide a reading apparatus which can protect a sensor unit and driver circuit unit from external factors such as static electricity, external light, and the like, which may cause damage and operation errors.
The present invention is directed to a reading apparatus (image reader 1) comprising a sensor module 3 which has a photosensor array 10 for optically reading an object to be detected, and a driver circuit unit (top gate driver 11, bottom gate driver 12, detection driver 13) for supplying a drive signal that drives the photosensor array, wherein a conductive film (static electricity protection portion 2) for discharging static electricity is formed on at least a portion of the surface of the driver circuit unit, as shown in FIG. 1.
According to the present invention, even when a fingertip charged with static electricity touches the vicinity of the driver circuit unit, since the static electricity protection portion shields the driver circuit unit, operation errors of and damage to the driver circuit unit can be prevented.
On the other hand, if an opaque conductive film is formed on the surface of the driver circuit unit, even when the driver circuit unit is exposed to external light, which comes from above the conductive film and contains ultraviolet rays and light in a given wavelength range that excites transistors of the driver circuit unit, the conductive film absorbs and/or reflects the external light, so that the external light can never enter the driver circuit unit. Therefore, operation errors of the transistors of the driver circuit unit due to incoming excitation light and their deterioration due to ultraviolet rays can be prevented.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.